Blinds equipped with a mechanical end stop system are known in the art. Best known are the so-called spindle & nut-end stops. A spindle & nut end stop system generally includes a threaded shaft, a wandering nut threaded on the shaft and at least one end stop member fixed on the shaft. For roller blinds and other blinds where a roller is rotated to wind and unwind a covering material about the roller, it generally the case that the nut is keyed to a driven portion of the blind and the shaft is stationary, such that when the blind is driven the nut rotates and is displaced in an axial direction along the threaded nut. When the nut reaches the end stop member the nut can no longer be displaced along the shaft and since the driven portion of the blind is keyed to the nut either directly or by way of the shaft, rotation of the driven blind portion will be stopped too.
When the driven member of a blind rotates with a certain speed the nut will reach the end stop at a considerably speed too. In order dampen the impact of the end stop system it is known to add a shock absorber.
A spindle & nut end stop system with shock absorber is described in U.S. Pat. No. 2,020,595 in relation to a spring driven roller blind. The end stop is set limiting the lifting of the roller blind. A spindle shaft (15) is stationary with respect to the roller (6) about which the blind material is to be wound. A travelling nut (24) is threaded to the shaft (15) and slidably keyed to the roller (6) such that rotation of the roller rotates the nut and it moves along the length of the threaded shaft. When the blind is wound about the roller up to a maximal height the nut impacts the end stop. In order to somewhat cushion an impact impulse, received by the end stop, a compression spring is interposed between a fixed stop and the movable nut.
Another type spindle & nut end stop with impact absorber for a roller blind is described in EP 210381. Here a torsion spring (25) is arranged to the end stop (22), such that the travelling nut (26) will engage the torsion spring directly. The friction between the travelling nut (26) and the torsion spring (25) prevents further rotation of the nut and thus of the blind roller (16).
Both of these systems can only impact the shock in one direction of operation of the blind, in these systems upon lifting of the blind.
Another problem is that springs to absorb the impact in direct contact with the end stop, so that the end stop is displaced by the impact of the travelling nut.